transmission fails to shift to high gear or overdrive on intermittent basis
I put that alone in a window to make it easy to hyperlink. The is a shift solenoid for O/D inside transmission, problem is I don't know which one. Click for full screen
Now, this one has all the info, but in Arabic. If you want to go to all the trouble of using Google translate you (we) can probably learn something http://www.mekshat.com/vb/showthread.php?t=352780&page=45
That one says: For whatever reason Toyota engineers programmed an over drive lockout to force you into a service bay and to protect the engine. Like me, you’re probably shaking your head in disbelief that something like not having a gas cap on can cause an OD lock out. Just leave your gas cap off, run it down below a 1/4 tank, hit the freeway and see what happens.
better focus than other schematic
By far and large the number one culprit for not shifting in to Overdrive is cold temperature. Lexus RX300’s will not shift into OD until the transmission fluid is up to operating temperature. This is a royal pain in the ass but is normal.. --Danny Maddox
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